Heating devices, more especially for motor vehicles



March 30, 1965 HEATING DEVICES, MORE ESPECIALLY FOR MOTOR VEHICLES FiledJuly 9, 1963 Fig. I

K. PANICK United States Patent 3,175,551 HEATING DEVICES, MOREESPECIALLY FOR MOTOR VEHICLES Karl Panick, Krailling, near Munich,Germany, assignor to Webasto Werk G.m.b.H., Munich, Germany Filed July9, 1963, Ser. No. 293,676

Claims priority, application Switzerland, July 25, 1962, 8,905 62 6Claims. (Cl. 126-116) The invention relates to heating devices operatedwith liquid fuel (and intended more especially for use in motorvehicles), of the kind having a tubular combustion chamber into which afuel-air mixture, delivered by a displacement blower, is fed through aninlet aperture, the displacement blower supplying all the air forcombustion. In addition there is provided an ignition device surroundedby a tubular protective casing, the axes of the protective casing andthe combustion chamber being substantially parallel.

Heating devices of this type can be of small dimensions and are stablein operation in respect of disturbances liable to originate from theeffect of headwind on the exhaust gas. Another advantage of thisconstruction is that it can be provided with long exhaust pipes, thussubstantially reducing installation problems. For these devicescombustion chambers have been developed comprising an annular space intowhich leads the pipe conducting the fuel-air mixture. In thesecombustion chambers, however, and particularly at temperatures below l00, the fuel-air mixture is difiicult to ignite.

The present invention aims at providing a heating device which retainsthe advantages of the above-described known type of heater but which canbe started easily even at low temperatures.

According to the invention the protective casing surrounding theignition device is disposed inside the combustion chamber (which ispreferably in the form of a cylindrical tube), and its axis is ofiset inrelation to the axis of said chamber in such a manner that the distancebetween the part of the combustion chamber wall accommodating thefuel-inlet aperture and the protective casing of the ignition device isgreater than the distance between the protective casing and the part ofthe combustion chamber wall which lies opposite to the inlet aperture.

On account of the off-setting of the protective casing of the ignitiondevice, and notwithstanding the large quantity of air entering thecombustion chamber from the displacement blower at high pressure ascompared with other types of blowers, more of the fuel, first impingingagainst the wall of the combustion chamber, becomes deposited on to theprotective casing, due to the barrier action of the wall of thecombustion chamber, which, viewed from the inlet aperture, lies behindthe protective casing.

' In order to obtain adequate build-up of fuel round the protectivecasing, the distance between the part of the combustion chamber walllying opposite the inlet aperture and the protective casing of theignition device should be not more than 4 mm., and preferably less than2 mm.

With regard to the offset location of the protective casing, thedistance between the combustion chamber axis and the axis of the tubularprotective casing should amount to at least one-fourth of the diameterof the inlet aperture for the fuel-air mixture. If the inlet aperture isnot circular, this dimension should be determined by the diameternecessary to provide a circular aperture of the same crosssection as thenon-circular inlet aperture. It is also of importance in a deviceaccording to the invention that between the protective casing and thecombustion chamber wall at the narrowest part of the combustion chamber,a distance of at least /2 mm., and preferably 1 mm., is pro- 3,175,551Patented Mar. 30, 1965 ice vided so that the annular form of that partof the combustion chamber is not entirely lost, because in that case theflow conditions would be aifected.

Experiments have shown that the delivery of the fuel on to theprotective casing is also advantageously promoted if the axis of theinlet aperture forms with the axis of the combustion chamber an acuteangle which preferably amounts to at most 70, but to not less than 20",while the point of intersection of said axes is nearer than the inletaperture, to the exhaust gas pipe connected to the combustion chamber. Aswirl plate may be provided in the part of the supply pipe for thefuel-air mixture directly before the inlet aperture.

Ease of ignition at low temperatures may further be increased by a sievedisposed inside the protective casing and lying, as viewed from thecombustion chamber, behind a row of holes provided in the protectivecasing.

One example of a heating device according to the invention will now bedescribed with reference to the accompanying drawings, which will revealstill further features and advantages of the invention.

In the said drawings, FIGURE 1 shows a heating device according to theinvention in side elevation and partly in section, and

FIGURE 2 a section through the heating device shown in FIGURE 1, alongthe line II-H.

As can be seen in the heating device illustrated in FIG- URE l, adriving motor 3 in a casing 2 located at one side of a heater 1 drives ablower 4 to circulate air to be heated, and a displacement blower 5which delivers combustion air and liquid fuel through the pipe 6 and ahollow screw 7 to a combustion chamber 8, in which a sparking plug 10surrounded by a protective casing 9 is installed. The passage 11 for thehot gases of the burnt fuel lies inside the heat transmitter 1 and atits end near to the burner forms a part of the combustion chamber, andit extends rectilinearly to an exhaust gas outlet 12 to which an exhaustpipe may be connected.

The air to be heated passes through the inlet aperture 13 into theblower 4, and from the latter is delivered into the heating passage 14which encircles the hot gas passage 11. In the air passage 14 the airflows to the outlet 17 over ribs 16 provided therein on a cylindricalsurface 15, and then through a pipe (not shown) into the compartment ofthe vehicle which is to be heated.

In the cylinder 15 safety passages 18 and 19, which, as can be seen inFIGURE 2, extend, with other passages 20 and 21, parallel to the axis ofthe combustion chamber 8 and the hot gas passage 11, are intended toprevent the exhaust gases from entering the air passage 14 in the eventof a leak developing in the passage 11.

As can also be seen from FIGURE 1, the sparking plug 10 and its casing 9are formed as a unit with a screwthreaded body portion for screwing intoan aperture in the combustion chamber. The casing 9 is otfset inrelation to the axis of the combustion chamber so that at the Side ofthe combustion chamber opposite to the inlet 7 the wall of the casing 9is close to the wall of the combustion chamber. At this point theclearance should not be more than 4 mm., and is preferably less than 2mm.

An annular sieve may be fitted within the protective casing 9 but forclarity is not shown in the drawing. This sieve may be situated, asviewed from the combustion chamber 8, behind a row of holes 23 in theprotective casing 9 and may extend to a point near to the sparking plug10.

A swirl device in the form of a helix may be fitted inside the hollowscrew 7 and may have approximately the form of a mincer spiral butsubstantially shorter, and this also is not shown in the drawing, forclarity.

As shown in FIGURE 1 the disposition of the inlet mouthformed by ,theiendwof the hollow ,screwi7 wisisueh that on the one hand part of it isin close proximity to the protective casing 9 but another part is at agreater distance therefrom than? the part of the combustion cham-.

ber {wall 1 24 nearestthe, protective. -casing 9.- The. greater ispacing between the Wall part 25 of. the combustion.cham-- ber8nwhich=support-s the -inlet aperture andthe casing-9 as compared. withthat vbetweenlche part 24.of-the.lcombustion. chamberwall..lying,,.opposite. the. inlet aperture and 7 the casing i9 .can.also, be clearly ,seen, from .FIGURE 2,. which, also shows.themoon-shaped @cross-sectioni of thev combustion chamber which 'isaifeaturfe of. the invention.

The invention, is. not restricted. to ,the ,exemplary embodimentdescribed, but, may the. modified and, added tov in a various wayswithout departing from; thes'copeaof the invention as defined in theappended claims. 1 V

WhatI claim is:

1. A liquid ,fuel operated,heating,device=comprising in.

combination: a

a heatrvexchanger including: means defining a first channel havingsacircular crosssectionah area, for combustion gasesv and; means defininga second, channel having an, annular, crossrsectionaljarea substantially.sur-

rounding said firstchannelgfor aheattransfer mediumy.

a burner having,anvoutenwallacoaxial. andin direct. communication withsaid first channel means, said.v

outerrwallvhavingva fuel-linlehaperture therein, a

tubular protective casing disposed within said outerwall andhaving itsaxis-oifset with respect to --the axis of zsaid outeniwall, theouter-surface1of said tubular; casing; and 'the-:inner surface. of saidouter wall defining jan;annularicombustion chamber wherebytheuradial'tdistance' between the portions of the inner surface of said.outer wallycontaining the fuel,

inletiaperture and the+outersurface of -'said tubular casing is greatervthan the distance between the diametrically: opposed portions of-theinner surface of said outerwalland theouter surface of said tubularcasing respectively, andianiignitiontdevice disposed,

the diameter of the fueli'nlet. aperture for thefuel -air mixturea 4.v Aheating device as claimed inclaim "1, wherein between said protectivecasing.. and said outer wall [at the narrowest .point ofv thecombustion. chamber a spacing of 0.5 mm. to 1 mm. isprovideda 5.:Aheating device as claimed inclaim-l, wherein the axisof'the fuel inletaperture-formstwithl the axis of the combustion chamber an acute angle,the point of intersection of the -said-axis being closer to saidignition device than to said means defining said first channel"communicat- I ingwith'said combustion chamber.;

6:: Ai'heatinglidevice asclaimed :inuclaim 5, wherein the anglebetween.the axes of the combustion chamber and the 1 fuel :inletapertureiamounts to. not more than, and not less than 20?; V

ReferencesCited ing'th'e file "of this patent UNITED'STATES PATENTS"1,867,324 Mullan July 12, 1932 2,286,857 Holthouse June 16, 19422,721,607; Damon et a1. Oct. 25, 1955 3,071,183 Rau Jan.- 1, 1963

1. A LIQUID FUEL OPERATED HEATING DEVICE COMPRISING IN COMBINATION: AHEAT EXCHANGER INCLUDING MEANS DEFINING A FIRST CHAMNEL HAVING ACIRCULAR CROSS SECTIONAL AREA FOR COMBUSTION GASES AND MEANS DEFINING ASECOND CHANNEL HAVING AN ANNULAR CROSS SECTIONAL AREA SUBSTANTIALLYSURROUNDING SAID FIRST CHANNEL FOR A HEAT TRANSFER MEDIUM; A BURNERHAVING AN OUTER WALL COAXIAL AND IN DIRECT COMMUNICATION WITH SAID FIRSTCHANNEL MEANS, SAID OUTER WALL HAVING A FUEL INLET APERTURE THEREIN, ATUBULAR PROTECTIVE CASING DISPOSED WITHIN SAID OUTER WALL AND HAVING ITSAXIS OFFSET WITH RESPECT TO THE AXIS OF SAID OUTER WALL, THE OUTERSURFACE OF SAID TUBULAR CASING AND THE INNER SURFACE OF SAID OUTER WALLDEFINING AN ANNULAR COMBUSTION CHAMBER WHEREBY THE RADIAL DISTANCEBETWEEN THE PORTIONS OF THE INNER SURFACE OF SAID OUTER WALL CONTAININGTHE FUEL INLET APERTURE AND THE OUTER SURFACE OF SAID TUBULAR CASING ISGREATER THAN THE DISTANCE BETWEEN THE DIAMETRICALLY OPPOSED PORTIONS OFTHE INNER SURFACE OF SAID OUTER WALL AND THE OUTER SURFACE OF SAIDTUBULAR CASING RESPECTIVELY, AND AN IGNITION DEVICE DISPOSED WITHIN SAIDTUBULAR CASING; A POSITIVE DISPLACEMENT BLOWER FOR FURNISHING THE TOTALAIR AND FUEL NECESSARY FOR COMBUSTION TO SAID BURNER THROUGH A SUPPLYLINE COMMUNICATNG WITH SAID FUEL INLET APERTURE; AND DRIVING MEANS FORSAID POSITIVE DISPLACEMENT BLOWER.